I am going to be doing a family photoshoot for my friend. I am an ameture and just learning but I know that she is going to want an 8x10 and 5x7. I was wondering if there is anything special I need to do in order to be able to print those sizes. I know there is a crop factor or somthing in the camera or that I shoudl take a certain pixel but I am so confused on what settting I should put my camera on in order to be able to print those sizes. Can anyone help. I will shoot in apeture p mode if that matters.
Thanks

1. Keep the camera from shaking and focus correctly (tripods work well, but unnecessary if the shutter speed is fast enough). Take your time, but not so much that you get phony smiles. I like to take a 2nd shot after the first because they relax (but before someone looks away). In fact 5 or 10 shots of the same scene may provide a better choice.
2. Pay attention to the background. Contrary to popular belief, trees should not grow from your mother-in-law's head.
3. Avoid harsh direct sunlight and don't have the sun directly behind them.
4. For a portriat; it's better to use aperture (Av) priority and set it to the lowest possible number. This will blur the background.
5. If you're using a digital SLR and there's not much light (dusk or cloudy), then bump up the ISO.
6. Use about 70 to 120mm (35mm equiv) lens. This puts you at a good distance to avoid proportion problems (fat torso, big nose, etc). Take it from about eye level. Have them lined up fairly evenly.
7. Most photographers use a flash for portriats, but if you don't know anything at all about photography, hmmmm, let's just say that it is possible to mess up a photo by incorrectly using a flash but point-and-shoot flash photography is also feasible (now, "P" mode is more desirable). Really depends on the lighting and what lens you're using.
8. Practice some in similar lighting settings before your shoot.
9. Do not succumb to the temptation of showing the lesser results. Just pick the few best and go with them.
10. Editing software can make for improvements and is recommended. Often it allows you to keep the best capture that has a few technical errors.

There's about 50 other general tips one could give. Too many tips may just scare you away. Very likely; if you take 50 to 100 shots, you'll have at least a few really good ones. Please share your results!

Here's one I took of my mom Saturday. I can see where a few improvements could be made, but overall I'm happy with it. Notice that the blurred background brings out the subject. I haven't had time to edit it yet - mainly to erase the purple CA spots.
http://FLASHME.smugmug.com/photos/108498963-L.jpg